Manufacture of cigarettes and other tobacco-filled rod-like articles

ABSTRACT

A device which scans the density of successive in crements of a cigarette rod produced in a cigarette making machine, is used to control the mean weight of the tobacco in that rod with a view toward maintaining substantially constant the number of cigarettes produced having a weight falling below a preselected level. Signals produced by the scanner are used to control the quantity of excess tobacco removed from the filler stream formed therein by a trimming device, thereby controlling the quantity of tobacco placed in said rod.

United States Patent 1 Labbe et a1.

[ MANUFACTURE OF CIGARETTES AND OTHER TOBACCO-FILLED ROD-LIKE ARTICLESInventors: Francis Auguste Maurice Labbe,

Neuilly-sur-Seine, France; Gordon Francis Wellington Powell, Deptford,London, SE8, England Molins Machine Company Limited, London, EnglandFiled: Mar. 13, 1970 Appl. No.: 19,286

Assignee:

[30] Foreign Application Priority Data Mar. 14, 1969 Great Britain13,685/69 U.S. Cl. 131/21 B, 131/21 D, 250/833 D Int. Cl. A24c 05/34Field of Search 131/21 R, 21 A, 21 B,

[5 6] References Cited UNITED STATES PATENTS 5/1960 Lanore 131/21 Dl/l954 Broekhuysen et al .[131/21 B [111 3,738,376 1 June 12, 19732,357,801 9/1944 3,082,323 3/1963 3,242,321 3/1966 2,952,262 9/19602,937,280 5/1960 2,800,131 7/1957 3,242,927 3/1966 3,259,746 7/1966Blunt 131/21 R X Primary Examiner-Joseph S. Reich Attorney-Craig,Antonelli & Hill [57] ABSTRACT A device which scans the density ofsuccessive in crements of a cigarette rod produced in a cigarette makingmachine, is used to control the mean weight of the tobacco in that rodwith a view toward maintaining substantially constant the number ofcigarettes produced having a weight falling below a preselected level.Signals produced by the scanner are used to control the quantityofexcess tobacco removed from the filler stream formed therein by atrimming device, thereby controlling the quantity of tobacco placed insaid rod.

7 Claims, 4 Drawing Figures TE/M ER PATENIED JUN 1 2191s SHEEIT 1 i]? 2Mg My 1 MANUFACTURE OF CIGARETTES AND OTHER TOBACCO=FILLED ROD-LIKEARTICLES In cigarette making machines there is commonly provided ascanning device, for example a Beta ray device, for detecting thedensity of the cigarette rod as it passes the scanning device and forcontrolling the amount of tobacco forming the cigarette, with a view tomaintaining the tobacco content in the cigarettes constant as far aspossible. For example, the tobacco content in terms of weight per unitlength may be varied by varying the distance of a trimmer from a suctionband carrying the tobacco filler, for example as described in U.S. Pat.No. 3,089,497. The tobacco filler is commonly enclosed in a continuousweb, usually of paper, which forms the cigarette wrapping.

With some cigarette making machines, for example the Molins Mark 8machine, it is possible to obtain a low figure of standard deviation(for example 2.5

percent) where a: T

W being the nominal weight of the cigarettes and W being the actualweights of each of N cigarettes. Accordingly it has been possible to setthe nominal weight (i.e. the mean weight as controlled by the Beta rayor other measuring device) at a relatively low value which, owing to thelow standard deviation, nevertheless resulted in substantially all thecigarettes having a weight above a threshold value T which was a valuebelow which a cigarette manufacturer would want no more than a certainvery small percentage of cigarettes (for example about 0.135 percent) tobe. The actual percentage below T which could be tolerated depended uponany given manufacturers requirements in relation to the desired qualityof his cigarettes, as did the chosen value of T. The threshold weight Tmay for example be 7% percent below the mean weight.

One aspect of the present invention is concerned with a departure fromthat previous concept of cigarette manufacture. This departure is basedon a con-- cept of varying the mean weight of the cigarettescontinuously in order to maintain substantially constant an operatingcharacteristic relating to the number of cigarettes having a weightbelow a predetermined threshold weight T which may or may not be thesame as the threshold weight T specified previously. In one preferredsystem according to this invention, all cigarettes having a weight belowthe value T are automatically ejected from the production line. Thesecigarettes may subsequently simply be stripped so that the tobaccofilling can be re-used. Alternatively these underweight cigarettes mayin principle be subjected to a further test, for example a continuousfilling-pressure test, (e.g. as described in U.S. Pat. No. 3,633,590),after which they are ejected and stripped only if they have also failedthe further test.

This invention enables a cigarette making machine to operate at a lowermean filling weight than hitherto, with a consequent saving of tobacco.

This will be further explained with reference to the accompanyingdrawings. In these drawings:

FIGS. 1 and 2 are graphs showing weight distributions of cigarettesduring manufacture;

FIG. 3 is a diagrammatic drawing of parts of one apparatus according tothis invention; and

FIG. 4 is a block diagram of a system wherein several cigarette makingmachines are controlled by a central computer.

FIGS. 1 and 2 are graphs showing cigarette weight (X) againstproportional distribution (Y). That is to say Y represents theproportion of cigarettes which have any given weight X.

The curve C in FIG. 1 is a curve corresponding to a cigarette makingsystem designed to produce only a very small and insignificant number ofcigarettes below a threshold weight of T, the mean weight in this casebeing Ml. In a system operating according to the present invention themean weight may at any given moment be for example M2, giving a curve ofcigarette distribution C2. With this curve C2 there is an area Al (shownshaded) representing the number of cigarettes which have a weight lessthan T. These underweight cigarettes may according to this invention beejected and stripped so that the tobacco contained in those cigarettescan be re-used. The important point to note, however, is that M2 is lessthan M1, so that cigarette manufacture according to the curve C2 willuse less tobacco while still ensuring that substantially no cigarettesare produced with a weight less than T.

In controlling a cigarette making operation according to this invention,the mean weight is preferably varied automatically in order to keepsubstantially constant the number of cigarettes having a weight whichfalls below the value T. This control is desirable because the standarddeviation of the cigarette making machine may increase or decreaseslightly from time totime, giving a flatter or sharper curve C2.Variation in standard deviation may for example be caused by variationsin the quality of the tobacco or in the tobacco moisture content ortemperature. If the mean weight were kept constant at M2, a temporarilyflatter curve (i.e. resulting from a higher standard deviation) wouldresult in more cigarettes falling below T in weight. This is illustratedby FIG. 2, which again shows the curve C2 (as in FIG. 1) and shows alsoa flatter curve C3 which represents the weight distribution given by ahigher standard deviation but with the same mean weight M2. It will beseen that the shaded area A2, representing the number of cigaretteshaving a weight of less than T, is larger than the area A1 in FIG. 1. Ina preferred system according to the present invention, when the standarddeviation increases in this way, the mean weight is automaticallyincreased to a value M3; this gives a weight distribution curve C4 belowwhich the area to the left of the threshold weight line T isapproximately the same as the area A1. On the other hand, during timeswhen the standard deviation is lower than that represented by the curveC2 (i.e. giving a sharper weight distribution curve) there is a smallernumber of cigarettes falling below the weight T, and the mean weight ispreferably, according to this invention, reduced automatically so as torestore the number of cigarettes below T to the same value as before, asrepresented by the area Al.

Various ways of computing the standard deviation B rette in turn. Asseen in FIG. 4, in the case of a cigarette factory including a number ofcigarette making machines, each machine may have a recorder unit forrecording information (e.g. relating to cigarette weights) .which istransmitted at regular intervals to a central computer serving all themachines, for example as described in (1.8. application Ser. No.840,279, filed July 9, 1969. This computer receives information fromeach machine in turn, for example about once a minute, and calculatesthe standard deviation; this computer may also take account of otherfactors (for example the moisture content and temperature of thetobacco) in sending back a signal to each machine to change the meanweight if necessary.

The standard deviation may be derived by counting up the number ofcigarettes obtained from a given length of the cigarette rod which havea weight coming between two predetermined limits. For example the lowerlimit may be the threshold weight (or zero) and the upper limit may be avalue greater than the mean weight and can be chosen so that theproportion of cigarettes coming between these two limits bears anapproximately linear relationship to the standard deviation.

As an alternative to the arrangement described, in which the standarddeviation of each machine is computed from information transmitted atintervals to a central computer, each machine may have provision forcomputing continuously the standard deviation on the basis, for example,of a predetermined number of the last cigarettes to have been made up toany particular instant.

In general, as an indication of a possible mode of operation accordingto this invention, the threshold ratio S may be approximately equal to3, where S (M2 T)/.

One problem which arises in carrying out this invention on the basis ofcigarette weight detection is that, where the standard deviation is say2.5 percent, the instrument error in detecting the cigarette weight maybe as high as 1.1 percent. There is consequently what may be termed alow signal to noise ratio, for example 25:1. 1. The ratio would bebetter (i.e. higher) if the instrument error were smaller, but it is noteasy to reduce the instrument error or noise, especially in the case ofa Beta ray or other scanning device which is arranged to'have a fastresponse so as to be sensitive to variations between very shortincrements of the cigarette rod, for example of the order of l or 2 mm.in length.

A preferred system according to this invention, in which an improvedsignal to noise ratio can be obtained, is one in which the mean weightof the cigarettes is controlled by sensing the density of shortcigarette sections of predetermined length, for example to 12 mm. Theshort sections are preferably the end portions of the cigarettes. Forexample, in the case of filter-tipped cigarettes, the end portions maybe at the untipped ends of the cigarettes (i.e. remote from the filter).Alternatively, the arrangement may be one in which the cuts separatingadjacent cigarettes pass through the centers of the end portions. Theend portions may be filled with tobacco at a greater density than theremainder of the cigarettes. The standard deviation of the tobaccofilling in the end portions may be of the order of say 5 percent. Thenoise or instrument error in reading ends density is higher than forcigarettes as a whole, for example, 1.65 percent, but

the signal to noise ratio (e.g. 521.65) is nevertheless better than inthe case of a control based on the cigarette as a whole. Consequently,according to this method, fewer satisfactory cigarettes (on the basis ofends quality) will be rejected and fewer unsatisfactory cigarettes willbe allowed to proceed. Moreover it is significant that this method ofcontrol directly governs the ends quality which is important to theconsumer.

According to another aspect of this invention the density signal foreach cigarette or cigarette end (or for each increment) is not taken asan absolute reading but is assessed with reference to a running meanreading taken from a number of adjacent cigarettes. For example a timedelay device may be used so that each signal is taken with reference toa mean value based on the signals derived from two or more upstreamcigarettes (or increments) and two or more downstream cigarettes (orincrements); alternatively the reference point may be the mean of thelast three or more cigarettes or increments. The mean reading from theadjacent cigarettes may be used as a reference from which to determinethe cigarette mean relative density. The actual reference point mayhowever in fact be based on an absolute value with a running correction(i.e. a bias in one direction or the other) derived from the meanreadings of the adjacent cigarettes. By this means a degree ofcompensation can be obtained for short-term variations in tobaccofilling power. For example, if the filling power were to droptemporarily owing to an increase in the proportion of shorts, with aconsequent increase in the mean weight, a cigarette which is somewhatlighter than the mean of the few adjacent cigarettes containing the samesort of tobacco might still be above an absolute threshold weight, butwould be correctly rejected on the basis of a comparison with the meansince it would be inadequately filled having regard to the low fillingpower of its tobacco; in other words it would be liable to be too soft.The converse occurs where the tilling power of the tobacco istemporarily higher than average; that is to say, comparison with themean of the adjacent cigarettes may save a slightly light cigarette frombeing ejected where it is in fact sufficiently firm to be accepted.

FIG. 3 shows an example of a system according to this invention forvarying the mean weight of the tobacco in the cigarette rod in responseto the mean density of the end portions.

As shown in FIG. 3, a continuous cigarette rod 2 (i.e. before it is cutinto cigarette lengths) passes through a guide tube 4 which has openingsthrough which Beta rays from a source 6 pass. After passing through therod, the beam of Beta rays enters a radiation detector which, in theexample shown, is an ionization chamber 8 comprising a shell 10 and anelectrode 12 which is electrically insulated from the shell. In additionthere is a balance unit comprising a radiation source 6A and anionization chamber 8A which is similar to the ionization chamber 8. Theamount of radiation reaching the chamber 8A is controlled by means of amovable absorption member 14 which in the arrangement shown is pivotallymounted at 16. I

A DC. potential is connected across terminals 18 and 20 on the shells ofthe ionization chambers. Consequently at a point 22 on a conductorconnecting the electrodes 12 and 12A there is a signal of which thestrength depends upon the density of the cigarette rod. The signal at 22is fed via an amplifier 24 and a control input 26 to a point 28connected to two discriminator circuits 30 and 32. These discriminatorcircuits are sensitive respectively to positive and negative signals.Each is connected to a relay 34 or 36 which controls the connection of avoltage supply to a reversible electric motor 33. When the signal at 28becomes positive or negative by more than a predetermined amount,signifying that the rod density is too low or too high, one or otherrelay is operated by the appropriate discriminator circuit so as todrive the motor 38 in one direction or the other so as to correct therod density. The motor 38 may for example control the position of atobacco trimmer 50 as already mentioned.

From the output of the amplifier 24 there is a connection to a switch 40which opens and closes rapidly under the control of a rotating cam 42.The cam rotates at a speed corresponding to one revolution per cigarettelength and is arranged to close the switch while each cigarette endportion is passing through the scanning device (i.e. past the radiationsource 6). The signal from the end portions is thus transmitted to acomputer 44. This computer, as already mentioned, may calculate thestandard deviation in various ways; it thus provides an output signal tothe control input 26 so as to vary the mean weight. In other words,under the control of the computer, the control input introduces apositive or negative signal (as the case may be) so as to change themean weight of the tobacco in the rod, for example by moving the trimmer50; i.e., the mean position of the trimmer is changed.

Instead of the control from the computer being introduced by means ofthe control input 26, it may for example be exercised by moving theabsorption member 14 of the balance unit. The member 14 may for examplebe movable into different positions by means of an electric servo motorin the well-known manner conventionally provided in control systems. Inthis case the member 14 may for example be in the form of a disc mountedto rotate about an axis parallel to the beam from the radiation source6A, the edge of the disc being so shaped (i.e. like a cam) as tointersect the beam by a variable amount depending upon the angularposition of the disc.

Downstream of the scanning device the rod is cut into cigarette lengthsby means of a cut-off device (not shown). Still further downstream thereis an ejector device 52 of standard configuration for ejectingcigarettes of which the ends have a density falling below the thresholdlevel. The ejector device may also eject overheavy cigarettes.

What we claim as our invention and desire to secure by Letters Patentis:

l. A method of making cigarettes or the like comprising enclosing atobacco filler in a continuous web to form a continuous rod adapted tobe cut into cigarette lengths, detecting the density of those portionsof the rod intended to become cigarette end portions by means of ascanning device which is arranged in a position along the path of therod and gives output signals relating to the density of the tobaccofilling in the rod, the output corresponding to the density of theintended cigarette end portions, varying the amount of tobacco placed inthe cigarette rod in response to said output signals to maintainsubstantially constant the number of cigarette end portions having amean density which falls below a predetermined level.

2. A method according to claim 1, including chopping the output signalsfrom the scanning device into a sequence of pulses representing thedensities of successive short increments of the rod.

3. A method according to claim 1, including ejecting cigarettes havingend portions of which the average density is below a predeterminedlevel.

4. A method according to claim 1, including comparing the density signalfor each intended cigarette end portion to the mean density of a fewadjacent intended cigarette end portions.

5. Apparatus for making cigarettes or the like comprising means forwrapping a continuous web around a tobacco filler to form a continuouscigarette rod adapted to be cut into cigarette lengths; means forvarying the mean weight of the tobacco filler; a scanning device whichscans the cigarette rod and is arranged to provide output signals atintervals timed so as to correspond to portions of the rod intended tobecome end portions of the cigarettes; means for repeatedly computingthe mean density of the intended end portions; and means forautomatically varying the mean density of the tobacco filler in responseto the computed mean density of successive end portions so as tomaintain constant the number of cigarette end portions obtained from agiven length of rod having a mean density which falls below apredetermined level.

6. A method of making cigarettes or the like comprising enclosing atobacco filler in a continuous web to form a continuous rod adapted tobe cut into cigarette lengths, detecting the density of the tobacco insaid rod with a scanning device arranged along the path of the rod toprovide outputs signals related to the density of successive linearincrements of the tobacco in said rod, comparing the signal from thescanning device for each linear rod increment to the mean of signalsfrom a number of adjacent increments, and controlling the mean weight ofthe tobacco entering said rod in response to the results of said signalcomparing.

7. Apparatus for making cigarettes or the like, cornprising means forenclosing a tobacco filler in a continuous web to form a continuouscigarette rod adapted to be cut into cigarette lengths, a scanningdevice arranged along the path of the rod to provide output signalsrelated to the density of successive linear increments of the tobacco insaid rod, means for comparing the signal from the scanning device foreach linear rod increment to the mean of signals from a number of adjacent increments, and means for varying the mean weight of the tobaccoentering said rod in response to the output of said comparing means.

i l i

1. A method of making cigarettes or the like comprising enclosing atobacco filler in a continuous web to form a continuous rod adapted tobe cut into cigarette lengths, detecting the density of those portionsof the rod intended to become cigarette end portions by means of ascanning device which is arranged in a position along the path of therod and gives output signals relating to the density of the tobaccofilling in the rod, the output corresponding to the density of theintended cigarette end portions, varying the amount of tobacco placed inthe cigarette rod in response to said output signals to maintainsubstantially constant the number of cigarette end portions having amean density which falls below a predetermined level.
 2. A methodaccording to claim 1, including chopping the output signals from thescanning device into a sequence of pulses representing the densities ofsuccessive short increments of the rod.
 3. A method according to claim1, including ejecting cigarettes having end portions of which theaverage density is below a predetermined level.
 4. A method according toclaim 1, including comparing the density signal for each intendedcigarette end portion to the mean density of a few adjacent intendedcigarette end portions.
 5. Apparatus for making cigarettes or the likecomprising means for wrapping a continuous web around a tobacco fillerto form a continuous cigarette rod adapted to be cut into cigarettelengths; means for varying the mean weight of the tobacco filler; ascanning device which scans the cigarette rod and is arranged to provideoutput signals at intervals timed so as to correspond to portions of therod intended to become end portions of the cigarettes; means forrepeatedly computing the mean density of the intended end portions; andmeans for automatically varying the mean density of the tobacco fillerin response to the computed mean density of Successive end portions soas to maintain constant the number of cigarette end portions obtainedfrom a given length of rod having a mean density which falls below apredetermined level.
 6. A method of making cigarettes or the likecomprising enclosing a tobacco filler in a continuous web to form acontinuous rod adapted to be cut into cigarette lengths, detecting thedensity of the tobacco in said rod with a scanning device arranged alongthe path of the rod to provide outputs signals related to the density ofsuccessive linear increments of the tobacco in said rod, comparing thesignal from the scanning device for each linear rod increment to themean of signals from a number of adjacent increments, and controllingthe mean weight of the tobacco entering said rod in response to theresults of said signal comparing.
 7. Apparatus for making cigarettes orthe like, comprising means for enclosing a tobacco filler in acontinuous web to form a continuous cigarette rod adapted to be cut intocigarette lengths, a scanning device arranged along the path of the rodto provide output signals related to the density of successive linearincrements of the tobacco in said rod, means for comparing the signalfrom the scanning device for each linear rod increment to the mean ofsignals from a number of adjacent increments, and means for varying themean weight of the tobacco entering said rod in response to the outputof said comparing means.